Improvement in cut-off valves



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AM. pHoro-urne. co. NAI. ssssssssssssssssss UNTTED STATES Errore@ PATENTROBERT STEWART, OF ELMIRA, NEW YORK.

IMPROVEMENT IN CUT-OFF VALVES.

To all whom t may concern:

Be it known that I, ROBERT STEWART, of Elmira, Chemung county, in theState of New York, have invented a certain new and useful Machine forOperating the Cut-Oft' Valves of Steam-Engines; and I do hereby declarethat the following is a full and exact description thereof', referencebeing had to the accompanying drawings, and to the letters of referencethereon marked.

In the drawings, Figure l is a side elevation, showing the valve-crankin a vertical position, as it stands when the valve-ports are closed.Fig. 2 is also a side elevation, but showing the parts as they standwhen the ports are wide open and the steam cut oft' at full stroke. Fig.3 shows the valvecrank. Fig. 4 is the weighted yoke which bears downupon the arms of the valvecrank so as to close the ports. Fig. 5 showsthe operatingcrank, to which the eccentric of the engine is attached andoscillates upon the valve-stem. Fig. 6 shows the yoke for regulating thebite of the pawls, and is operated bythe governor.

To enable those skilled in the art to make and use my invention, I willdescribe its construction and operation. y My invention consists inconstructing the machine hereinafter described for the purpose ofoperating a cut-oft valve for steam-engines. This object I attain bymeans of an arrangement simpler, cheaper, and more effective than anyheretofore known.

A represents the valve, the induction being at l and the eduction at 2.I make no claim to the construction of the valve, but prefer to use abalanced valve similar in construction to the valve patented to meheretofore.

B is the valve-stem.

O is the valve-crank. which is provided with I lateral arms a a. Thiscrank C is keyed to the valve-stem, and it is provided with a shortvertical arm, c, extending upward, the upper surface of the end of thisarm being described by a radius having its center at the center of thevalvestem. The outer corners, w of this Varm should be faced with steelwhere they meet the friction of the pawls.

D is aV weighted yoke, having arms d d at its lower end to rest upon thecurved arms a t of the crank C and make it return to its verticalposition when relieved from the bite of the pawls. The stem D of thisyoke D passes upward through a socket, E, in the curved support E',which is axed to the valve-chest.

D2 is a heavy ball keyed to the upper end of the stem D', and isprovided with a cylindrical extension having an air-chamber,D3, in it.The socket E acts as a stationary piston, the chamber D3 falling andrising around it. There is a small opening, c, from the chamber outwardfor the escape of the air, which is extended to act as a spring toprevent jarring by the sudden fall of the arms d d upon the arms a c.

F is the three-armed operating-crank, which is made to oscillate uponand around the valvestem by means of the eccentric, which is attached tothe button-stud g at its lower end. The upper end of the crank Fbranches out with two arms, F and F2, to the ends of which are pivoted,at t', the pawls G and G.

G and G are two pawls, respectively pivoted at t' to the crank-arms Fand F2. These pawls are formed in conformity with the arc whose radiusis at the center of the crankaxis, so that the under side of both pawlscorresponds to and slides over the upper end of the arm c of thevalve-crank C.

o-o o are studsvnear the toe of the pawls and projecting backward asufficient distance to rest upon the operating-yoke.

H is the operating-yoke, which moves upon and embraces the journal-boxof the valvestem. At its lower end it is pivoted to the lever I, whichis pivoted at V. The outer end of lever I is connected to the governor.The upper part of the yoke H is formed into an A or double-inclinedplane, h, upon which the studs o of the pawls rest, the rise and fall ofthe plane h correspondingly raising or lowering the pawls.

In operating my invention the valve is properly attached to the engine,and the steam is admitted at full pressure from the boiler. In a stateof rest the weighted yoke D presses down upon the arms c of thevalve-crank C, so as to keep it'vertical and close the valveports. Assoon as the steam is let into the valve I oscillate the valve-crank O byhand a few times, so as to open the valve-ports and let steam enoughinto the cylinder to start the machinery and operate the governor. Theaction of the governor, through lever I, is to raise or lower theoperating-yoke H and its plane h. When the governor is lifted the yokeis depressed, and when the governor is depressed the yoke is lifted. Asthe yoke rises or falls, so rise or fall the pawls G G, whose studs orest upon the top of the yoke; and the rise and fall of the pawlsdetermine the degree ot bite which they have upon the corners a: of thevalvecrank C. The engine being at work and its eccentric upon thereturn-stroke, as shown in Fig. 2, it will be seen that the pawl Gl ismade to push against the corner a; of the valve-crank C so as to openthe valve-ports.

- As the crank (l is pushed by the pawl the stud o of the pawl graduallyrises up upon the curved plane 7L, so that at the instant the steam isto be cut oft' the pawl shall be raised above and escape from the cornerof the crank, which will then be instantly forced into the Verticalposition, closing the ports by the weighted yoke D, which presses uponthe crank-arms a. At the instant that the pawl and crankcorner becomedisengaged the crank moves back to become vertical and close the ports,while the pawl goes in the opposite direction, sliding upon top ofthecrank, so as to allow the eccentric 'to complete the stroke. This beingdone, it will be found upon the forward stroke that the pawl G is, inturn, ready to instantly act in like manner upon the other corner, an,of the crank. In like manner the two pawls G and G alternately pushagainst the opposite corners of the valvecrank, pushing it more or lessto the right or left, and correspondingly cutting o' with more or lesssteam, in proportion to the degree of bite of the pawls against thecrank-corners.

When the governor is at its highest elevation the yoke will bedepressed,and the pawls will have their greatest hold upon the corners,and the crank will be pushed the greatest distance, and more steam willbe admitted, and the steam will be cut oft' almost at full stroke. Justthe reverse of these incidents will occur when the governor is at itslowest position, and the steam will be cut oli' almost as soon as itenters the cylinder.

lt will readily be seen that my invention is simpler, cheaper, and moreeffective in its construction and operation than any device heretoforeknown for this purpose.

Having fully described my invention, what I claim as new, and desire tosecure by Letters Patent, is-

1. The valve-crank C, provided with corners and arms a, substantially asdescribed, when used in combination with the pawls G G', or

their equivalent, and the Weighted yoke D d,

or its equivalent, substantially as and for the purposes specified.

2. The weighted yoke dD D D2, constructed and operating substantially asdescribed, and in combination with the arms a, socket E, and air-chamberD3, substantially as specified.

3. The operating-crank F F F2, constructed andl operating substantiallyas specified, in combination with pawls G G' and valve-crank C, for thepurposes specified.

4. The pawls G G, constructed and operating substantially as described,in combination with the regulating-yoke H h, valve-crank C, andoperating-crank F F' F2, substantially as and for the purposesspecified.

5. The regulating-yoke H h, constructed and operating substantially asspecified, in combination with the pawls G o G o, substantially as andfor the purposes specied.

6. The combined construction and arrangement of the weighted yoke D andvalve-crank C for the purpose of closing the ports, substantially asdescribed.

7. The arrangement of all the parts above described.

ROBERT STEWART.

Witnesses:

JN0. H. McGUrcHEN, Jo C. CLAYTON.

